If you use clear finger nail polish on the ball joints it will help tighten them up and make the figure sturdier, also the Zenitsu KO isnt a strict Zenitsu clone it recycles parts from Tanjiro which is why the Hayori looks weird, 1 piece from Zenitsu and 1 from Tanjiro which is weird and his inner frame is actually from Nezuko.
guys if its broken there is figma arm and leg joints i think the arm joint is standard figma leg joint if that helps your welcome and do a vid on it might help me in the future